Mobile radio communication systems have progressed through three generations including analog (first generation), digital (second generation), and multimedia (third generation). Third generation systems are sometimes associated with Universal Mobile Telecommunication Systems (UMTS). One example of a UMTS radio access network is the UMTS Terrestrial Radio Access Network (UTRAN) which has been specified in the Joint Standardization Projection identified as 3GPP (the Third Generation Partnership Project). In UTRAN, data generated at higher layers is carried over the radio interface with transport channels. These transport channels are mapped in the physical layer to different physical channels. The physical layer is required to support variable bit rate transport channels, to offer bandwidth-on-demand services, and to multiplex several services to one connection. In multimedia communications, other services such as e-mail, Internet access, video, and other services may be provided in addition to voice service.
When mapping transport channels to the physical channels, there are several mechanisms used to support variable bit rate transport channels and multiplexing of several services to one user connection. Each transport channel is accompanied by a Transport Format Indicator (TFI) every Transmission Time Interval (TTI) when data is expected to arrive for the specific transport channel from higher layers. The physical layer combines the TFI information from different transport channels to the transport format combination indicator (TFCI). The TFCI is transmitted in the physical control channel to inform the receiver which transport channels are active for a current frame. The TFCI is then decoded at the receiver, and the resulting TFI is given to higher layers for each of the transport channels active for the connection.
There are two types of transport channels: dedicated channels and common channels. A dedicated transport channel (e.g., DCH or DSCH) carries all of the information intended for a given user coming from layers above the physical layer including data for the actual services as well as higher layer control information. The data rate on a dedicated transport channel can change on a TTI basis. A dedicated channel is mapped onto two physical channels. The dedicated physical data channel (DPDCH) carries higher layer information including user data. The dedicated physical control channel (DPCCH) carries the necessary physical layer control information. These two dedicated physical channels are needed to support efficient variable bit rate in the physical layer. In the uplink (UL) direction, the bit rate of DPCCH is constant, whereas the bit rate of DPDCH can change from frame to frame. In the downlink (DL) direction, the DPCCH and the DPDCH are time-multiplexed on a constant rate physical layer.
Variable data rates may be implemented by a rate matching operation using rate information sent with the transport format combination indicator (TFCI) transmitted on the DPCCH for the current DPDCH frame. In other words, for every ten millisecond frame, the TFCI information decoded from the DPCCH frame is used to obtain the bit rate and channel decoding parameters for DPDCH. At the transmitter, rate matching is used to match the number of bits to be transmitted to the number available in a single frame and must take into account the number of bits coming from other transport channels that are active in a particular frame. Higher layers provide a semi-static parameter called the Rate Matching Attribute (RMA) to control rate matching between different transport channels. The rate matching attribute is used to calculate the rate matching value when multiplexing several transport channels for the same frame. By adjusting the rate matching attribute for each transport channel, it is ensured that an amount of data sent on this transport channel can efficiently be mapped on the physical layer.
Radio interface protocols are used to set up, reconfigure, and release radio bearer services provided in UTRAN. The protocol layers above the physical layer are called the data link layer (layer 2) and the network layer (layer 3). The layer 3 protocol is called Radio Resource Control (RRC) and belongs to the “control plane” (as opposed to the “user plane”). RRC messages carry the parameters required to set up, modify, and release Radio Access Bearers (RABs) and to perform channel switching. Each RAB “bears” one or more lower level, radio bearers (RBs), and each RB is mapped onto a corresponding transport channel.
The present invention is concerned with RRC signaling associated with the configuration of dedicated transport channels (e.g., DCHs). When a connection to a user equipment is initially established, and a radio access bearer is set up with one or more radio bearers, a physical radio channel configuration is set up that corresponds to the dedicated transport channels associated with each one of the one or more radio bearers. Certain parameters are specified in the radio channel configuration such as spreading factor, channel bit rate, coding, etc. The radio channel configuration also has a certain rate matching attribute established. During the lifetime of the connection, some aspect of the connection may be modified. Examples include a new service being added to the connection, an existing service being deleted from the connection, or some aspect of the channel is reconfigured, e.g., the rate of transport radio channel is modified. As a result, there is a need to reconfigure the rate matching attribute for the overall connection to accommodate the modification. However, the current 3GPP standard requires that the rate matching attribute for a transport channel in the connection can only be changed by reconfiguring the entire transport format set for this transport channel. This reconfiguration must take place even if the transport format set need not be reconfigured, i.e., nothing in the TFS changes.
Unnecessary reconfiguration is not only time consuming, it also requires unnecessary signaling which is particularly disadvantageous given scarce radio bandwidth resources. As new services are introduced, the number of transport channels defined for a particular connection will increase. This unnecessary reconfiguration of a transport format set for each transport channel leads to reduced capacity in the system as well as increased call establishment time. Redefining the transport format set unnecessarily decreases the capacity of the system by sending needless signaling over the air interface every time a new service is set up or released or some other aspect of the channel is changed, e.g., channel switching. Furthermore, procedure execution times are all increased since more transport blocks have to be transported towards the user equipment due to the increased probability of data retransmisssions. Lengthy signaling procedures could become disadvantageous for the end-user because of the increase in call establishment time and/or rate-switching execution time. Channel switching and the introduction of new transport channel rates may therefore also be adversely affected by this unnecessary signaling. In this case, the channel switching referred to is performed between two different dedicated channels (DCH-to-DCH).
The present invention solves these problems by providing the possibility to configure or reconfigure a rate matching attribute for a given transport channel without having to perform unnecessary transport format configurations/reconfigurations. A connection with a mobile radio is established using a configuration of a radio channel that specifies a first transport format. When some aspect of the connection is to be changed, the radio channel configuration will be reconfigured, but not entirely or unnecessarily. The reconfiguration may result from a new service being added to the connection, a service for the connection being removed, or some aspect of the radio channel configuration being modified, e.g., channel-rate switching, etc. As a result of the reconfiguration, one or more rate matching parameters associated with the connection are configured without having to configure the first transport format set. A rate matching algorithm is used to control an amount of data sent over the reconfigured radio channel per unit time based on one or more reconfigured rate matching parameters and one or more transport format.
Consider the following example. A first connection service for the mobile radio is established, and the radio channel is configured using a first transport format parameter and a first rate matching parameter. Thereafter, a second connection service is added that is associated with a second transport format parameter and a second rate matching parameter. The radio channel configuration is advantageously reconfigured to incorporate the second connection service with its second rate matching attribute without having to reconfigure the first transport format parameter.
As applied to a UTRAN specific example, a first setup message associated with the connection is sent to establish a first radio access bearer between the UTRAN and User Equipment (UE). The first setup message includes one or more first transport format parameters and one or more first rate parameters. A second setup message is sent to establish a second radio access bearer between the UTRAN and the UE. The second setup message includes one or more second transport format parameters, the one or more first rate parameters, and one or more second rate parameters. The first and second rate parameters are reconfigured in response to the second setup message but without having to reconfigure the first transport format parameter. Different example messaging formats are described below.